The present invention relates to electrical connectors, and more particularly to electrical arc suppression when the electrical connectors are separated from each other under load.
Power and signal distribution connectors mechanically and electrically connect at least two conductors at, ideally, the lowest possible power loss. Connectors are not designed to make and break an electrical circuit. Devices such as switches, relays and contactors are designed to switch current/voltage circuits. Nevertheless, during their service life, connectors can be plugged/unplugged under load many times (i.e. xe2x80x9chot pluggedxe2x80x9d). Very often this disconnection under load occurs when physically switching off the power in advance would be considered time-consuming and inconvenient. Also, connectors in automotive power networks are plugged and unplugged under load during diagnostic procedures, fuses are plugged at short circuit conditions, and so forth. Under some circumstances in the above situations, the connector suffers no significant damage with multiple engages/disengages. Other times, just one disconnect will damage the terminals beyond repair. In other words, under specific conditions, a long arc may be generated at engage/disengage, which may cause extensive terminal erosion. This erosion may damage the physical shape of the terminal, preventing re-engagement or proper terminal contact forces after assembly. Additionally, the electrical arc may have serious consequences for the environment or nearby personnel.
FIGS. 1A and 1B depict a pair of matable electrical connectors 10, wherein the male terminal 12 thereof has just been separated from the female terminal 14 thereof, and the tips of the terminals are presently within the terminal proximity zone Z. By xe2x80x9cterminal proximity zonexe2x80x9d is meant a zone length over which an electrical arc is most prone to arise when the terminals are subjected to an applied voltage (that is, when under load), which length may vary depending, for example, upon circuit load and atmospheric conditions. An electrical arc 16 leaps between the closest tips 12t, 14t of the terminals 12, 14, taking a most direct path therebetween. Because a most direct path is taken, the arc energy is maximal, resulting in potential for terminal erosion and for possible personnel injury.
Accordingly, it would be highly desirable if such arcs could be suppressed (quenched).
As shown at FIGS. 2A and 2B, it is well known that if a wire 20 is located between attracting magnets 22, 24 so as to be inside the magnetic field B, and if a current I is flowing along the wire, then a force is applied to the moving electrons by the magnets, referred to as the xe2x80x9cLorentz Forcexe2x80x9d. The direction of the force depends upon the direction of the magnetic field B and the direction of the current I, as shown. The resulting force F applied to the wire depends upon the magnitude of both the current I and the magnetic field B, the length of the wire exposed to the magnetic field, and the relative orientation between the wire and the magnetic field, given by:
F=IlB sin xcex8,
where l is the length of wire exposed to the magnetic field B and xcex8 is the angle between B and I, as shown by FIG. 2. When the angle xcex8 is ninety degrees (that is, I is perpendicular to B), sin xcex8 equals one and the force F is a maximum. When the angle xcex8 is zero degrees (that is, I is parallel to B) sin xcex8 equals zero and the force F is a minimum (equal to zero).
It would be desirable if somehow the above discussed Lorentz Force could be adapted to suppress electrical arcing when connectors are connected/unconnected under load.
The present invention provides electrical arc suppression when terminals under load are connected/unconnected via an applied magnetic field causing the arc path to be lengthened, with the consequences that the voltage necessary for the arc to be sustained is increased and the arc energy is decreased.
An electrical arc may be generated between terminals (including electrodes, contacts, etc.) when both the voltage and the current exceed certain minimum values. These minimum values are determined by the electrode material (e.g. silver 12V/0.4A, and carbon 20V/0.01A). In this regard, a magnetic field electrical arc suppression assembly according to the present invention includes at least one magnet placed adjacent the location (terminal proximity zone) of initial/final touching of mating connector terminals. The magnetic field produced the at least one magnet pervades the space occupied by the air gap between the terminals (the terminal proximity zone) such that as the terminals are brought into contact or separated from contact and the circuit is live, the tendency of an electrical arc to arise and be sustained is suppressed (quenched) by the magnetic field applying a force on the moving electrons as the arc commences. This force causes the electrons to take a curved (or otherwise longer) path across the air gap rather than take a straight-line path. Because a curved path is longer than a direct (straight line) path, a higher arc voltage is required to sustain the arc and the arc energy is diminished, thus suppressing (quenching) the arc, and thus greatly reducing the energy of the arc.
The at least one magnet may, for example, be in the form of a single magnet or a pair of diametrically opposed, attracting magnets. The at least one magnet may be of the permanent type, or may be of the electromagnet type. A magnetic circuit is provided via a yoke, as for example composed of a ferromagnetic material, to minimize reluctance of the magnetic circuit and thereby optimize the magnetic field conditions in the air gap of the terminal proximity zone during engage/disengage of the terminals.
The arc suppression (quenching) effect of the magnetic field according to the present invention is not limited by choice of the location of the at least one magnet. For example, it is possible to have the at least one magnet either integral with, or unconnected with, the connector. In other words, the at least one magnet may be integrated into the structure of the connector, be attached to a stationary part of the connector (e.g., fuse box), or be connected to a movable part of the connector or another component (e.g., a wiring harness) or some combination thereof. It is important that the magnetic field in the terminal proximity zone be oriented as close as possible to perpendicular in relation to the direction of the electrical current. Also, since the arc suppression performance of the magnetic field is dependent upon the strength of the magnetic field, a stronger magnet gives a better arc suppression (quenching) performance.
The present invention includes all possible methods of packaging the at least one magnet, as for example by molding, spraying, assembling, etc. Further, where the electromagnet type is used, the current therefore may be from a circuit carrying current through the connectors, or may be from a circuit external to the connectors. Additionally, the aforedescribed magnetic field suppression of connector separation arcing may also be applied at component terminals used to connect relays, fuses, electronic modules, motors, resistors, capacitors, inductances, lamps, etc.
Accordingly, it is an object of the present invention to provide suppression of electrical arcing between separating/connecting terminals under load via an applied magnetic field in the air gap between the terminals.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.